In e.g. automotive applications, it is desirable to have a warning system to indicate to a driver that a lamp of a lighting system, in particular tail lighting and/or break lighting, is defective. In response to the warning, the driver may replace the defective lamp.
A known prior art system requires a test mode or the like. For example, each time the lighting system is switched on or when a car is started, the lighting system is checked. However, if a lamp breaks during use, no signal is generated. Further, known prior art systems use complex and expensive circuitry in order to detect a defective lamp.
Moreover, a known prior art warning system is not suitable to be used with an LED. In particular, when an LED is dimmed, for example driven by a DC-DC converter circuit employing pulse width modulation (PWM) dimming, the known prior art system is not suitable to detect a defective LED.